A Mayoral spokesman is quoted in the Telegraph pointing out the "enormous long-term advantages" on offer in London's financial centre - but is Boris really going to have an impact on such a huge decision by a global megacorp? Financial organisations threaten to quit the UK every time a government mutters something about increasing regulation to prevent, say, a crisis that would drag the nation's economy through the mire. But they rarely do - and besides, these matters are decided on more than a whim and a flounce.
HSBC, for example, reviews its HQ location every three years - the bank is originally from Hong Kong and Shanghai (check the initials) and only moved to London following their takeover of Midland Bank. They're listed on the Hong Kong Stock Exchange as well as London and given the explosion in the Chinese economy... HSBC going 'back home' would have a massive impact on employment in the City and Treasury revenue, but we don't think it would necessarily mark the start of a massive banking exodus - or even that it's a given whether the world's local bank will leave at all (that's an awful lot of experienced staff to replace).
And as for Boris? If HSBC really are hoping to emotionally blackmail the UK into not tightening regulation and raising taxes, we're not sure what the blond one's bluster can do. HSBC must be laughing all the way to the bank.